Means for separating granular material



Dec. 29, 1959 c. L. KINGSBURY, JR 2,919,024

MEANS FOR SEPARATING GRANULAR MATERIAL Filed Jan. 28, 1957 2 Sheets-Sheet l INVEN TOR. (A/5 75/2 1.. k/A/assueme Dec. 29, 1959 c. L. KINGSBURY, JR 2,919,024

MEANS FOR SEPARATING GRANULAR MATERIAL Filed Jan. 28, 1957 2 Sheets-Sheet 2 lulu-ll Mann-II "7 IN V EN TOR.

115 1): 2/ M MM 5 6m 33 55 ATTOENE ya CHESTER L. K/N65BUEKJP.

United States Patent MEANS FOR SEPARATING GRANULAR MATERIAL Chester L. Kingsbury, Jr., Babbitt, Minn., assignor to Reserve Mining Company, Silver Bay, Minn., a corporation of Minnesota Application January 28, 1957, Serial No. 636,619 3 Claims. (Cl. 209-159) This invention relates to a method and means for separating two components of respectively different specific gravities from a moving stream of conglomerate granular material. Said moving stream may come to the separating means either as a dry, granular mixture, or as an aqueous slurry, although, as will appear, water is added in the separation zone as a necessary adjunct of the invention.

While in many possible applications, for example coal washing, mineral dressing, or the like, the invention is useful in the separation of two components of different specific gravities, it will be described, for purposes of present exemplification and illustration, in connection with the separation of ferrous ore concentrates from the usually accompanying siliceous gangue or tailings.

As is familiar to those skilled in the art of beneficiating originally relatively low grade iron ores, such at tac onite, only a minor fraction, perhaps one third of the ore from the mine, is actually recoverable iron bearing, the balance being some non-recoverable ferrous and nonferrous tailings, mostly silicates. The iron-containing fraction, in a specific exemplification here identified as magnetite, is of considerably higher specific gravity than the siliceous tailings or waste product, and various processes are now in commercial application for beneficiating the ore, such as by magnetic separation in a moving slurry. By reason of the aforesaid difference in specific gravity it is often economically advisable to use, in conjunction with magnetic separation, certain interspersed hydro-separation steps involving gravity displacement in an enclosure through which the ore slurry passes. Such enclosure is often conventionally termed a wash box, and such term may be used on occasion herein.

An object of the present invention is to provide 'a novel and improved process and apparatus for the separation of heavier and lighter fractions from a liquid slurry.

A further object of the invention is to provide a process and apparatus for decreasing circulating loads in a continuous ore beneficiation system having closed circuit portions.

A further object of the invention is to provide a process and apparatus for lessening abrasive wear on all surfaces contacted by an advancing stream of mixed granular components of differing specific gravities.

A further object of the invention is to provide an ore beneficiation process and apparatus which results in a decreased expenditure of horsepower per ton of finished ore concentrate.

A further object of the invention is to provide a novel and improved process and apparatus for taconite ore beneficiation which removes silica, phosphorus, calcium, magnesium, sulphur or other deleterious gangue components, improves the grade of the finished product, and yields a more desirable feed ore for blast furnaces.

A further object of the invention is to provide a novel and improved wash box for use in series with a magnetic separator and with rotary mill grinding means, and

wherein interposition of said wash box in the flow system relieves the grinding circuit of an amount of tailings which would otherwise be imposed on said circuit; which allows an increased load of ore concentrate on the grinding circuit; and which beneficiates the feed to subsequent operating elements in the flow system so as to allow said elements to operate more efiiciently.

A still further object of the invention is the removal of gangue slimes from the circuit.

Other objects and advantages .will be apparent from a study of the following description of one embodiment of the invention in conjunction with the accompanying drawings, in which:

Fig. 1 is a perspective view of an enclosure embodying.

my invention, parts being broken away to reveal internal structure.

Fig. 2 is a top plan View of the enclosure shown in Fig. 1.

Fig. 3 is a vertical sectional view taken on the line 33 of Fig. 2, but showing an ore slurry being separated in the enclosure.

Figs. 4 and 5 are sectional views, greatly enlarged, showing respectively an air pipe and a water pipe, the views being taken on the lines 44 and 5-5 of Fig. 2.

The enclosure or wash box best shown in Figs. 1, 2 and 3 has a bottom wall 20, two side walls 21 and 22 and two end walls 23 and 24. End wall 23, sometimes herein identified as at the entry end, is of shorter vertical dimension than end wall 24, at the discharge end, and consequently the bottom wall 20 slopes downwardly at an angle herein set at about forty-five degrees towards a low point or underilow discharge zone 20a which is provided with one or more discharge spigots or nipples 25, four being here shown.

Extending transversely beyond end wall 24- at its upper edge is a trough 26, best seen in Figs. 1 and 3. End wall 24 is cut away along a substantial portion of its transverse width to provide an overflow weir 24:: whereby to afford an overflow discharge of liquid from the enclosure into trough 26, and trough 26 is provided with a pipe 27 through which overflow slurry is discharged froin the enclosure. The upper edge of the weir 24a establishes the liquid level for the enclosure as long as liquid flows into the enclosure in an amount sufficient not only to satisfy the total capacity of the underflow discharge pipes 25, but also to provide an additional volume of liquid to flow over weir 24a.

The entry end 23 of the enclosure has a feed slot 28, preferably extending along most or all of the wall Width, through which is fed a granular conglomerate, for example the discharge from a rod mill grinder or magnetic separator, said conglomerate having components of respectively different specific gravities. In this exemplification the conglomerate is a taconite ore containing magnetite, a heavier component, and lighter tailings which are mostly a siliceous gangue. This taconite, preferably in particles of about sixty mesh dimension or smaller, may enter the feed slot in dry granular form, or as an aqueous slurry. Without any pretense of quantitative accuracy, but merely for purposes of illustration, I have shown (in Fig. 3) the magnetite as dark rounded particles 29, and the siliceous tailings as dark triangular particles 30.

I have provided means for supplying jets of wash water, and jets of air, to simultaneously cooperate in separating the ore concentrate from the tailings by inducing turbulence in the aqueous slurry. The lighter and heavier components are discharged by respectively different paths.

A water header 33 enters through side wall 21 and extends the full width of the wash box immediately adjacent to the end wall 23 and below the feed slot 28. A

plurality of parallel branch pipes 34 are in liquid flow communication with header 33 and extend downwardly near but spaced from the bottom wall 20. The ends of these pipes preferably pass through end wall 24, and may have at their'ends removable caps 35 for occasional cleaning purposes. Pipes 34 are provided with a plurality of perforations 34a (Fig. 5) extending in rows along their full length, within the enclosure, and in the present instance each pipe has two such rows, spaced about forty-five degrees apart. Jets of water atsuitable pressure issue from these perforations, impinge against the enclosure bottom, dislodging material tending to settle thereon, and then produce rising currents and turbulence in the liquid body. As heretofore indicated'the volume of water must be sufficient to produce overflow across weir 24a as well as underflow through pipes 25.

The wash box is also equipped With means for directing jets of air upwardly within the liquid pool. In the present instance such means consists of a pair of air pipes 35, extending transversely across the enclosure between water pipes 34 and bottom, wall 29. Each air pipe has two rows of perforations 35a therein, spaced at about a forty-five degree divergence, this being preferred though not necessary. The perforations are directed generally upwardly, and air from a compression source (not shown) enters pipes 35 (Fig. 4) and discharges through the perforations in upward jets which materially increase the turbulence in the pool, aiding separation of the ore concentrates from the gangue in the granular conglomcrate. In Fig. 3 the air bubbles are shown as small plain circles 38, as destinguished from the dark circles 29 previously mentioned.

A bafile plate 37 extends transversely across the top I of the enclosure with its lower edge extending below the liquid surface. This has the effect of providing a zone of increased turbulence near the entry port, so as to disrupt the cohesive forces tending to bind the lighter and heavier particles together. The particles thus disrupted are free to be borne upwardly and over the upper level weir or downwardly through the lower level discharge spigots in accordance with their varying specific gravities. trated iron-containing particles to further grinding and separating steps, such means being merely schematically illustrated at 31 (Fig. 3). Other means 32 convey the waste products to any convenient disposal point.

The several significant factors may be varied to suit local operating conditions. The diameters and numbers of the underfiow spigots 25 may be varied with relation to the water supply to insure an adequate level of water in the pool. Air pressure and volume may be controlled to provide maximum desired agitation. The angle of the enclosure bottom 20 can be adjusted to suit the criti- Means is provided for routing the concencal angle of repose of the heavier constituent-as affected by the turbulent pool conditions. The perforations in the water and air pipes may be varied in dimension and in angular direction to suit the type of materials being separated.

Use of the process and apparatus as hereinabove described, and shown in the drawings, has the following attendant advantages, when used in ore beneficiation: It removes silica, phosphorus, calcium, alumina, magnesium compounds, sulphur compounds, and other deleterious gangue material, thereby improving the grade of the finished product, and affording a more desirable feed ore for blast furnaces. It lowers ore shipping products by producing more iron units per ton of finished product. Since the usable concentrates are later subjected to a filtering step for liquid separation, the use of the present invention improves filtering by removing gangue slimes which tend to block the filters and increase moisture in the filter cake. Improved filtering consequently lowers drying costs for pelletizing, sintering, nodulizing, and similar eventual operations.

When the present wash box is placed in a closed circuit flow operation with magnetic separators and grinding means such as ball mills, it decreases the circulating load by removing a greater percentage of tailings from the circuit. The grinding capacity can therefore be applied to a greater percentage of usable concentrate in 'further fine grinding operations. This necessarily per mits a decrease in the horsepo'wer-per-ton ratio of the an ished concentrate product. It lessens ,theabrasive Wear on equipment surfaces by removing more of the useless tailings at an early stage in the beneficiation process. Many other advantages might be asserted here, but, briefly, the features of greatest significance in the art are that the present invention relieves grinding mill circuits of a definite load of tailings; it allows an increased pay load to be fed to subsequent processing circuits such as grinding circuits; and it improves the grade of feed to finishing units, allowing the Whole process to operate more efiiciently.

While the invention has been described with special reference to ferrous ore beneficiation, the process and apparatus can obviously be also adapted to the separation of other granular agglomerates having components of diverse specific gravities at least one of which can be carried with an aqueous overflow discharge.

To illustratequantitatively the advantages of the pres ent invention, I tabulate the results of adapting my improved wash box to use in a closed circuit flow operation of the character mentioned in the second preceding paragraph. The test covers six individual days, asfollows:

Percent Percent Period re Tails Recovery Removed First Day 96. 27 3. 73 Second Day 96. 96 3. 04 Third Day 95. 94 4. 06 Fourth Day 98.96 1.04 Fifth Day 92. 93 7.07 Sixth Day 93. 37 6. 63

Average 4. 26

This average of 4.26% of tails removedrepresents a reduction of about 12.4 tons per hour in recirculating load in a plant unit where there is a total of about 290 tons per hour recirculating load. Such reduction of 12.4 tons per hour is a substantial amount and is quite. pleasing from an economic standpoint. The advantages of a decrease in recirculating load have heretofore been touched upon. A

What I claim is:

1. Means for separating a lighter component from a heavier component of a granular agglomerate, said means comprising an enclosure having a front Wall, a rear wall, two side walls, and a bottom wall, said bottom wall having a high end at said front wall and being inclined downwardly therefrom towards a low end at said rear Wall, said front wall having an inlet opening therein, said rear wall having an upper edge portion at a level lower than said side walls to thereby constitute an overflow weir, said bottom wall having at its low end a discharge opening,

means for admitting water to said enclosure in down- 2. Means as defined in claim 1 wherein said means for admitting water consists of a plurality of parallel water pipes, at least some of said pipes each having two rows of apertures directed generally downwardly, said two rows being peripherally spaced from each other at an angle of about forty five degrees.

3. Means as defined in claim 1 wherein said perforate air pipe means consists of at least two parallel pipes, each said pipe having two rows of apertures directed generally upwardly, said two rows being peripherally. spaced from each other at an angle of about forty five 1 degrees.

References Cited in the file of this patent UNITED STATES PATENTS Callow Mar. 12, 1918 Waterhouse July 13, 1920 Gahl July 20, 1920 Manegold May 20, 1952 Walker Nov. 4, 1952 FOREIGN PATENTS Australia Nov. 12, 1946 

1. MEANS FOR SEPARATING A LIGHTER COMPONENT FROM A HEAVIER COMPONENT OF A GRANULAR AGGLOMERATE, SAID MEANS COMPRISING AN ENCLOSURE HAVING A FRONT WALL, A REAR WALL, TWO SIDE WALLS, AND A BOTTOM WALL, SAID BOTTOM WALL HAVING A HIGH END AT SAID FRONT WALL AND BEING INCLINED DOWNWARDLY THEREFROM TOWARDS A LOW END AT SAID REAR WALL SAID FRONT WALL HAVING AN INLET OPENING THEREIN, SAID REAR WALL HAVING AN UPPER EDGE PORTION AT A LEVEL LOWER THAN SAID SIDE WALLS TO THEREBY CONSTITUTE AN OVERFLOW WEIR, SAID BOTTOM WALL HAVING AT ITS LOW END A DISCHARGE OPENING MEANS FOR ADMITTING WATER TO SAID ENCLOSURE IN DOWNWARDLY DIRECTED JETS AGAINST SAID BOTTOM WALL, IN AN AMOUNT SUFFICIENT TO MAINTAIN THEREIN A POOL HAVING A LEVEL IN LIQUID OVERFLOW RELATIONSHIP WITH SAID WEIR WHILE PERMITTING SIMULTANEOUS DSICHARGE OF LIQUID THROUGH SAID DISCHARGE OPENING, MEANS FOR DISCHARGING A STREAM OF AGGLOMERATE THROUGH SAID INLET OPENING, AND PERFORATE AIR PIPE MEANS EXTENDING TRANSVERSELY ACROSS SAID HIGH END OF BOTTOM WALL FOR ADMITTING A PLURALITY OF UPWARDLY DIRECTED-COMPRESSED AIR JETS POOL TO INDUCE TURBULENCE IN SAID POOL WHEREBY SAID LIGHTER COMPONENT OVERFLOWS SAID WEIR AND SAID HEAVIER COMPONENT IS DISCHARGED THROUGH SAID DISCHARGE OPNING. 